Light guide plate for uniformly scattering lights from point light source

ABSTRACT

A light guide plate that can uniformly scatter lights emitted from point light sources is provided. The light guide plate has a light exiting side, a reflection side opposite to the light exiting side, and a light entering side. On the light entering side, there are multiple miniature diffusing entities. Each of the diffusing entities has a curved surface and two slant surfaces extending from the two ends of the curved surface to the light entering side. The curved surface causes the lights from the light sources to undergo multiple-angled refractions. The two slant surfaces cause the lights from the light sources to undergo fixed-angled refraction in both left and right directions. As such, the lights emitted form the light sources could have wider incident angles and could be uniformly scattered into the light guide plate.

BACKGROUND OF THE INVENTION

(a) Technical Field of the Invention

The present invention generally relates to light guide plates ofTFT-LCDs, and more particularly to light guide plates that can uniformlyscatter lights from point light sources by widening the lights' incidentangles.

(b) Description of the Prior Art

A typical planar light source found in a TFT-LCD, as shown in FIG. 1,mainly includes a light guide plate 11, a reflection plate 12, a numberof diffusion films 13 and prism sheets 14, and lamps 15. As one of themost important components of the planar light source 1, the light guideplate 11 receives, transmits, and redirects lights emitted from thelamps 15.

As shown in FIG. 2, the light guide plate 11 is usually of a rectangularshape, having a light exiting side 111, a reflection side 112 oppositeto the light exiting side 111, and at least a light entering side 113 atthe flank. The lights emitted from the lamps 15 enter into the lightguide plate 11 via the light entering side 113, of which a portiondirectly leaves the light guide plate 11 via the light exiting side 111,and the other portion lands on the reflection side 112. The reflectionside 112, therefore, is configured with numerous dots 1121 on thesurface and the dots 1121 have increasingly higher distribution densityor larger surface area as they are located farther away from the lamps15, so as to reflect light as much as possible to the fight exiting side111.

Usually, cold cathode fluorescent lamps (CCFLs) or light-emitting diodes(LEDs) are used as the lamps 15 for the planar light source 1. Theapplication of CCFLs is simpler, as they are linear light sources. Onthe other hand, the application of LEDs is more complicated as they arepoint light sources. As shown in FIG. 3, the lights emitted from theLEDs 16 would have an incident angle when entering the light guide plate111 via the light entering side 113. There are, therefore, bright zones114 and dark zones 115 formed inside the light guide plate 11, dependingon whether they are within the coverage of the incident light. Althoughadding more LEDs 16 could eliminate dark zones 115, this is not asatisfactory approach as the additional LEDs 16 increase material cost,power consumption, assembly complexity, and the possibility of futuremalfunctioning.

Another approach has been proposed for eliminating dark zones. As shownin FIG. 4, the light guide plate 2 has a fight exiting side 21, areflection side 22 opposite to the light exiting side 21, and at least alight entering side 23 at the flank. The fight entering side 23 isconfigured to have a plurality of saw-toothed diffusing entities 231.The lights emitted from the LEDs 25, when passing through the slantsurfaces 2311 of the diffusing entities 231, are scattered to havelarger incident angles. The dark zones 24 inside the light guide plate 2are thereby reduced. However the approach has its own problem. As shownin FIG. 5, when lights emitted form the LEDs 25 passes thought thediffusing entities 231, they are refracted by the two slant surfaces2311 of each diffusing entity 231 and some of them would have alignedtraveling direction. These aligned refracted lights would add to eachother to form brighter lights 26, resulting in non-uniform lighting ofthe light guide plate 2. This phenomenon would limit the subsequentapplication of the light guide plate 2 and is not consistent with theuniform lighting requirement of the light guide plate 2.

SUMMARY OF THE INVENTION

The primary purpose of the present invention is to provide a light guideplate that can uniformly scatter lights from point light sources. Thelight guide plate of the present invention forms diffusing entities onthe light entering side of the light guide plate, so that lights emittedform the light sources could have wider incident angles and coulduniformly scatter into the light guide plate.

To achieve the objective of the present invention, each of the diffusingentities formed on the light entering side of the light guide plate hasa curved surface and two slant surfaces. The curved surface causes thelights from the light sources to undergo multiple-angled refractions inboth left and right directions.

In addition, the two slant surfaces cause the lights from the lightsources to undergo fixed-angled refraction in both left and rightdirections.

The foregoing object and summary provide only a brief introduction tothe present invention. To fully appreciate these and other objects ofthe present invention as well as the invention itself, all of which willbecome apparent to those skilled in the art, the following detaileddescription of the invention and the claims should be read inconjunction with the accompanying drawings. Throughout the specificationand drawings identical reference numerals refer to identical or similarparts.

Many other advantages and features of the present invention will becomemanifest to those versed in the art upon making reference to thedetailed description and the accompanying sheets of drawings in which apreferred structural embodiment incorporating the principles of thepresent invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective explosion view of a conventional planar lightsource.

FIG. 2 is a schematic side view of a conventional light guide plateshowing trajectories of lights.

FIG. 3 is a schematic top view of a conventional light guide plateshowing trajectories of lights from pint light sources.

FIG. 4 is a schematic top view of another conventional light guide plateshowing trajectories of lights from pint light sources.

FIG. 5 is another schematic top view of the light guide plate depictedin FIG. 4.

FIG. 6 is a perspective view of a light guide plate according to anembodiment of the present invention.

FIG. 7 is an enlarged schematic top view of a light guide plateaccording to an embodiment of the present invention showing trajectoriesof lights.

FIG. 8 is a perspective view of a light guide plate according to asecond embodiment of the present invention.

FIG. 9 is a perspective view of a light guide plate according to a thirdembodiment of the present invention.

FIG. 10 is a perspective view of a light guide plate according to afourth embodiment of the present invention.

FIG. 11 is a schematic top view of a light guide plate according to afifth embodiment of the present invention.

FIG. 12 is a schematic top view of the light guide plate depicted inFIG. 11 showing trajectories of lights.

FIG. 13 is a schematic top view of a light guide plate according to asixth embodiment of the present invention.

FIG. 14 is a schematic top view of a light guide plate according to aseventh embodiment of the present invention.

FIG. 15 is a perspective view of a light guide plate according to aneighth embodiment of the present invention.

FIG. 16 is a cross-sectional view along the A-A line as depicted in FIG.15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following descriptions are of exemplary embodiments only, and arenot intended to limit the scope, applicability or configuration of theinvention in any way. Rather, the following description provides aconvenient illustration for implementing exemplary embodiments of theinvention. Various changes to the described embodiments may be made inthe function and arrangement of the elements described without departingfrom the scope of the invention as set forth in the appended claims.

In the following, detailed description along with the accompanieddrawings is given to better explain preferred embodiments of the presentinvention. Please note that some parts in the accompanied drawings arenot drawn to scale or are somewhat exaggerated. It should be understoodthat this is for illustrative purpose, and is not intended to limit thepresent invention in any way.

Please refer to FIG. 6. As shown in FIG. 6, the light guide plate 3 is atransparent board. The light guide plate 3 has a light exiting side 31,a reflection side 32 opposite to the light exiting side 31, and at leasta light entering side 33.

The light exiting side 31 is where the lights form the light sources(not shown) are delivered. The reflection side 32 is configured to havemultiple dots (not shown) for reflecting lights emitted from the lightsources to pass through the light exiting side 31. The lights emittedfrom the light sources enter and travel inside the light guide plate 3via the light entering side 33. Please note that the light entering side33 is configured to have multiple miniature diffusing entities 331. Eachof the diffusing entities 331 has a curved surface 3311 and two slantsurfaces 3312 are extended from the two ends of the curved surface 3311to the light entering side 33.

Please refer to FIG. 7. As shown in FIG. 7, the lights emitted from thelight sources (LEDs 34), when passing through the curved surfaces 3311of the diffusing entities 331, would be refracted in various angles. Onthe other hand, the two slant surfaces 3312 produces fixed-angledrefraction to both left and right sides of the incident lights. Thefixed-angled refracted lights would, therefore, blended with themultiple-angled refracted lights so that the non-uniform lighting foundin prior arts is avoided. In other words, the diffusing entities 331according to the present invention could not only widen the incidentangles of the lights from point light sources but also could avoid thenon-uniformed lighting resulted from fixed-angled refraction.

As shown in FIG. 7, on the light entering side 33, there are small gapsbetween adjacent diffusing entities 331. To further increase thescattering effect, the diffusing entities 331 could be continuouslyarranged with no gaps left therebetween, as shown in FIG. 8.

In addition to having the diffusing entities 331 to bulge outward fromthe light entering side 33, the diffusing entities 331 could beconfigured to concave inward into the light guide plate 3, as shown inFIG. 9. The concaved, curved surface 3311 and slant surfaces 3312 widenthe incident angles of the lights from LEDs 34 and scatter the lightsuniformly inside the light guide plate 3, which is identical to how theprevious embodiments of the present invention work.

As shown in FIG. 9, there are small gaps between adjacent concaveddiffusing entities 331. Similar to FIG. 8, the diffusing entities 331could be continuously arranged with no gaps left therebetween, as shownin FIG. 10, to further increase the scattering effect.

The scattering effect of the previous embodiments could be furtherenhanced by forming multiple concaved, V-shaped diffusing grooves 331 onthe surface of the diffusing entities 331, as shown in FIG. 11. Thediffusing grooves 331 are aligned in parallel and extended from thereflection side 32 to the light exiting side 31. When lights emittedfrom the LEDs 34 pass through the light entering side 33, as shown inFIG. 12, they are not only scattered by the diffusing entities 331, butalso further scattered by the slant surfaces 3321 inside the diffusinggrooves 332.

In another embodiment of the present invention, instead of having aregular V shape, the diffusing grooves 332 could have an irregular Vshape, as depicted in FIG. 14, which could still achieve the samescattering effect.

In embodiments where there are gaps between adjacent diffusing entities331 on the light entering side 33, the gaps could also be configured tohave diffusing grooves 332 on the surface. In this way, the lightsemitted from the LEDs 34 would all undergo the scattering effect of thediffusing grooves 332.

Besides having diffusing grooves 332 on the light entering side 33, thediffusing grooves 332 could also be formed on the external surface ofthe light exiting side 31. In this way, the lights from the LED 34 arenot only scattered inside the light guide plate 3, but also furtherscattered when they leave the light guide plate 3 through the lightexiting side 31. As shown in FIG. 15, the diffusing grooves 332 on thelight exiting side 31 are parallel and aligned with the lights'traveling direction inside the light guide plate 3. FIG. 16 is across-sectional view along the A-A line as depicted in FIG. 15. As shownin FIGS. 15 and 16, the diffusing grooves 332 on the light exiting side31 are arranged with no gaps therebetween. In other embodiments, therecould also be gaps between adjacent diffusing grooves 332 on the lightexiting side 31.

It will be understood that each of the elements described above, or twoor more together may also find a useful application in other types ofmethods differing from the type described above.

While certain novel features of this invention have been shown anddescribed and are pointed out in the annexed claim, it is not intendedto be limited to the details above, since it will be understood thatvarious omissions, modifications, substitutions and changes in the formsand details of the device illustrated and in its operation can be madeby those skilled in the art without departing in any way from the spiritof the present invention.

1. A light guide plate having a board shape for uniformly scatteringlights from a light source, comprising: a light exiting side fordelivering said lights to outside of said light guide plate; areflection side opposite to said light exiting side for reflecting saidlights to change their course of traveling inside said light guideplate; and a light entering side at the flank of said light guide forreceiving said lights from said light source; wherein a plurality ofminiature diffusing entities are formed on the surface of said lightentering side, said diffusing entities have a curved surface and twoslant surfaces extended from two ends of said curved surface to saidlight entering side respectively.
 2. The light guide plate according toclaim 1, wherein said diffusing entities are continuously arranged andhave no gaps therebetween.
 3. The light guide plate according to claim1, wherein each of said diffusing entities has a plurality of V-shapeddiffusing grooves on the surface of said diffusing entity concavedtoward inside of said light guide plate, said diffusing grooves arealigned in parallel and extended from said reflection side to said lightexiting side.
 4. The light guide plate according to claim 1, whereinsaid diffusing entities are concaved toward inside of said light guideplate.
 5. The light guide plate according to claim 3, wherein saiddiffusing grooves are further formed on the surface of said lightentering side between said diffusing entities.
 6. The light guide plateaccording to claim 3, wherein said diffusing grooves are further formedon the external surface of said light exiting side, which are paralleland aligned with lights' traveling direction inside said light guideplate.
 7. The light guide plate according to claim 3, wherein saiddiffusing grooves have a regular cross-sectional shape.
 8. The lightguide plate according to claim 3, wherein said diffusing grooves haveirregular cross-sectional shapes.